Rotary tablet presses have usually a rotor, which contains a die plate with individual die bores, and an upper and a lower punch guiding. Upper and lower punches are guided in the punch guiding, which co-operate with the die bores. In addition, cams for the punches are arranged above and below the rotor. Further, at least one pressing station is associated to the perimeter of the die plate, which presses the punches against each other with at least one pressing roller, in order to press the powder-like material in the die bores together. Finally, a filling device belongs to a rotary tablet press also, which fills the die bores running along with powder material. The pressed tablets are subsequently moved out of the die bores with the aid of the lower punches, and are removed by a strip-off device. The rotor is driven by a suitable driving apparatus, mostly an electric motor. A housing surrounding the described parts forms a pressing room, which prevents dust generated in the pressing from arriving in the surroundings. Vice versa, the housing prevents also the intrusion of contaminations into the pressing room.
From DE 10 2004 040 163, the entire contents of which is incorporated herein by reference, it has become known to integrate the electric motor into the rotor, while the motor's rotor lying at the outside is splinedly connected with the inner wall of the tablet press rotor, and the stator is stationarily supported in a suitable way. For this embodiment, it is no more necessary that a rotor shaft has to be guided into the housing for instance, which is driven via a gear box by a driving motor situated remotely below, or that the housing surrounds the drive also. Thus, a sealing for the rotor shaft does no more apply.
The parts located in the pressing room have to be cleaned from time to time. For this reason, it has become known from EP 0 288 798, the entire contents of which is incorporated herein by reference, to connect the holders of cams which control the punches with stationary housing portions via detachable connecting means, and to connect them with the die plate by take-along elements such that after detaching the connecting means, the die plate can be lifted off from the driving shaft, together with the upper and lower punches and the cams. Thus, the rotor can be removed completely from the rotary tabletting machine, for performing a cleaning externally. Also, back fitting of the machine can be performed in this way, to another punch distribution or only for other punches, for instance. The removability of a rotor is also treated in EP 1 050 399 A2, the entire contents of which is incorporated herein by reference.
From U.S. Pat. No. 4,259,049, the entire contents of which is incorporated herein by reference, it has become known to essentially seal the proper pressing region for upper and lower punches by housing portions. A source of negative pressure is connected to the housing parts, in order to suck off the dust which is generated in the two pressing rooms. Air supplementation takes place from the outside via channels in the punch guidings. From U.S. Pat. No. 6,676,836 B2, the entire contents of which is incorporated herein by reference, it has further become known to encapsulate the rotor into an essentially sealed housing, in order to protect the pressing room or to prevent the dust generated in the pressing room from arriving in the outside. In this state of the art, it is also known to separate the rotor together with the enclosing housing from the remaining parts of the press, so that the unit can be transported to a cleaning station, in which all the cleaning processes are performed.
In order to achieve a sealing between the housing and the surroundings which is as good as possible, the already mentioned U.S. Pat. No. 6,676,863 the entire contents of which is incorporated herein by reference, provides lip sealings, which are mounted on the rotor and the upper and lower punch guiding, respectively, with the aid of a suitable holder, and which frictionally co-operate with the housing. A disadvantage of the dragging seals is that wear and heat generation take place.
The present invention is based on the objective to provide a rotary tablet press, in which an effective sealing, with little wear and little friction, of a housing of the rotor is achieved.